Polyisocyanurate-based syntactic coating for offshore applications

Abstract

A polyisocyanurate-based coating for offshore applications is provided. The coating is a syntactic coating, obtainable by reacting a polyisocyanate compound with a compound containing isocyanate-reactive hydrogen atoms in the presence of a trimerisation catalyst and hollow objects, at an isocyanate index of at least and preferably more than 2000.

Claims

1. A polyisocyanurate-based syntactic coating composition obtained by reacting a polyisocyanate compound with a compound containing isocyanate-reactive hydrogen atoms in the presence of a trimerisation catalyst and hollow objects, characterised in that the isocyanate index of the reaction is 2050 and the resulting coating has a water uptake of less than 5%, an elongation of more than 10% and a thermal insulating property of less than 0.18 W/mk, and the density of the coating composition is between 0.9 g/cm.sup.3 and 1.5 g/cm.sup.3 and wherein the compound containing isocyanate-reactive hydrogen atoms having an ethylene oxide content ranging from 5 wt. % to 30 wt. % is a polyether polyol selected from a polyethylene glycol, polypropylene glycol, polypropylene glycol-ethylene glycol copolymer, polytetramethylene glycol, polyhexamethylene glycol, polyheptamethylene glycol, polydecamethylene glycol and a polyol obtained by ring-opening copolymerisation of an alkylene oxide with an isocyanate-reactive initiator of functionality 2 to 8 or a polyester polyol obtained from the reaction of a polyhydric alcohol and a polybasic acid.

2. The polyisocyanurate-based coating composition according to claim 1, wherein the isocyanate index is in the range of 2050 to 7000.

3. The polyisocyanurate-based coating composition according to claim 1, wherein the hollow objects are hollow glass beads.

4. The polyisocyanurate-based coating composition according to claim 1, wherein the compound containing isocyanate-reactive hydrogen atoms has an ethylene oxide content of 5 to 15 wt. %.

5. A pipe for use as part of a pipeline suitable for offshore application, the pipe having an outer surface and at least one syntactic polyisocyanurate-based coating at said outer surface, said coating being as defined in claim 1 and having a water uptake of less than 3.5%.

6. The polyisocyanurate-based coating composition according to claim 2, wherein the isocyanate index is in the range of 2050 to 4000.

Description

(1) The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

(2) FIG. 1 is a schematical view of consecutive steps of a process for providing a pipeline suitable for offshore application according to the present invention.

(3) FIG. 2 is a schematical view of a radial cross section of a pipe being part of a pipeline suitable for offshore application according to the present invention.

(4) The present invention will be described with respect to particular embodiments. It is to be noticed that the term comprising, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression a device comprising means A and B should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

(5) Throughout this specification, reference to one embodiment or an embodiment are made. Such references indicate that a particular feature, described in relation to the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases in one embodiment or in an embodiment in various places throughout this specification are not necessarily all referring to the same embodiment, though they could. Furthermore, the particular features or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art from this disclosure.

(6) The following terms are provided solely to aid in the understanding of the invention.

(7) Syntactic coating is to be understood as a coating comprising hollow objects, typically of controlled size, such as hollow glass beads, embedded in a polymer matrix.

(8) The iso-index or isocyanate index is to be understood as the number of isocyanate groups of the polyisocyanate compound per 100 isocyanate-reactive hydroxyl groups of the isocyanate-reactive compound.

(9) The functionality of a polyisocyanate or polyisocyanate compound, or the isocyanate functionality, as such or as polymeric or prepolymeric polyisocyanates, refers to the average number of isocyanate groups per molecule, averaged over a statistically relevant number of molecules present in the polyisocyanate or polyisocyanate compound. In case the polyisocyanate compound comprises a plurality of different polyisocyanate components, the isocyanate functionality is equal to the average isocyanate functionality averaged over the plurality of different polyisocyanate components, taking into account the mass ratio of the plurality of different polyisocyanate components in said polyisocyanate compound.

(10) The isocyanate content, isocyanate value or NCO-value, means the ratio, expressed in percentages, of the molar mass of the isocyanate groups in the isocyanate or polyisocyanate component over the total molar mass of the isocyanate or polyisocyanate component. In case the polyisocyanate compound comprises a plurality of different polyisocyanate components, the isocyanate content, isocyanate value or NCO-value is equal to the average isocyanate content, isocyanate value or NCO-value averaged over the plurality of different polyisocyanate components, taking into account the mass ratio of the plurality of different polyisocyanate components in said polyisocyanate compound.

(11) The functionality of the isocyanate-reactive initiators or a component comprising isocyanate-reactive hydrogen atoms, is to be understood as the number of isocyanate-reactive hydrogen atoms per molecule initiator or per molecule component comprising isocyanate-reactive hydrogen atoms. In the case of a plurality of isocyanate-reactive initiators or a compound comprising a plurality of different components comprising isocyanate-reactive hydrogen atoms, this functionality is equal to the averaged functionality, averaged over the plurality of isocyanate-reactive initiators or the plurality of different components comprising isocyanate-reactive hydrogen atoms, taking into account the mass ratio of the plurality of isocyanate-reactive initiators or the plurality of different components comprising isocyanate-reactive hydrogen atoms present.

(12) With hydroxyl value of a component comprising isocyanate-reactive hydroxyl atoms is meant the value obtained using the formula:
OH=(56.1*1000*functionality of the component/molar weight of the component)

(13) With EO content of a component comprising isocyanate-reactive hydroxyl atoms means the part, expressed in weightl-percentage, of ethylene oxide, as compared to the total amount of the component comprising isocyanate-reactive hydroxyl atoms.

(14) The term DMTA modulus at a given temperature refers to the Young's modulus at this temperature, typically either room temperature of 23 C. or at 150 C., measured using the dynamic mechanical thermal analysis (DMTA) technique, ISO/DIN 6721-5 for measuring DMA in flexural mode, performed on a TA DMA 2980 device.

EXAMPLE

(15) According to the present invention, a number of different coatings were provided according to a formulation as set out in table 1.

(16) TABLE-US-00001 TABLE 1 Catalyst Iso and func- NCO amount EO tion- ISO value ref. ISO type Polyol type (% wt) (%) ality index (%) I* MDI based polyether 0.2% 15 2.2 960 19.3 prepolymer ethylene Dabco oxide TMR tipped triol II MDI based polyether 0.2% 15 2.5 2250 31.4 ethylene Dabco oxide TMR tipped triol III MDI based polyether 0.2% 15 2.1 2000 27.5 prepolymer ethylene Dabco oxide TMR tipped triol IV MDI based polyether 0.2% 15 2.3 2058 28.6 prepolymer ethylene Dabco oxide TMR tipped triol V* MDI based polyether 0.2% 15 2.2 620 13.0 prepolymer ethylene Dabco oxide TMR tipped triol *comparative coatings

(17) The components are combined and used to provide a coating on e.g. a steel pipe, to be used for exploitation of deep sea oil wells. Some properties are set out in table 2.

(18) TABLE-US-00002 TABLE 2 DMTA DMTA Thermal modulus modulus Water uptake Density conductivity at 23 C. at 150 C. after 1000 h at ref. (g/cm.sup.3) (W/mK) (MPa) (MPa) 90 C. (%) I* 0.9 0.126 400 120 9.0 II 0.9 0.118 1200 1100 3.8 III 0.9 0.112 960 840 4.2 IV 0.9 0.105 1000 900 1.8 V* 0.9 / 110 30 14 *comparative coatings

(19) An example of a process for providing a polyisocyanurate-based coating on a surface of, in this particular example the outer surface of, a pipe of a pipeline, is illustrated in FIG. 1.

(20) In a first step 100, a pipe 101 is heated and brought to a temperature of about 80 C.; this may be done e.g. by induction or radiant heating. The pipe 101 is provided in step 110 with two end fittings 102, one at each side. In step 120, the pipe 101 with end fittings 102 is enclosed by a mould 121, such as in this embodiment, between two shells 122 and 123 of a tubular mould. The mould defines a space 124 in which the coating is to be cured.

(21) The space 124 of the mould 121 is filled, as is shown in step 130 with the coating material 131 having a formulation as set out above. The coating material 131 may e.g. be provided in the mould 121 via an inlet 125.

(22) The mould 121, including the pipe 101 and the coating material 131 is given time in order to cure the coating material 131 in the mould 121, as is shown in step 140.

(23) After curing, the mould 121 is removed in step 150, and the so-obtained demoulded pipe 152 comprises the pipe 101 and end fittings 102, which pipe outer surface is provided with a coating 151.

(24) The resulting pipe 152, of which a radial cross section is shown in FIG. 2, may form part of a pipeline suitable for offshore application. The pipe has an outer surface 153 which is provided by the polyisocyanurate-based coating 151. The coating may have a density of more than 0.6 g/cm.sup.3 and a water uptake of less than 3.5%. The thickness T of the coating, this is the largest distance between the surface 105 of the pipe 101 and the outer surface 153 of the coating 151 in radial direction 160, may range up to 50 cm, e.g. from 10 to 30 cm. The formulations as set out in the table 1 above may be used to provide the coating, providing the properties as set out in table 2 as well.

(25) It is to be understood that although preferred embodiments and/or materials have been discussed for providing embodiments according to the present invention, various modifications or changes may be made without departing from the scope and spirit of this invention.